The present invention pertains to instruments and methods for use in delivery of compositions, such as therapeutic fluids, through a tissue while minimizing exposure of the tissue to the compositions. More particularly, the invention pertains to treatment of a targeted tissue within an area of healthy tissue, and more particularly, to a multi-body apparatus and method capable of delivering compositions to a target tissue mass, such as, for example, a tumor, in the otherwise healthy tissue of a body organ, with minimum loss or exposure of the composition to the healthy tissue. The invention is particularly directed to multi-body apparatus capable of delivering compositions to a target tissue, such as brain tumor, while minimizing or preventing the exposure of healthy brain tissue to compositions that could potentially harm the healthy tissue.